There are a number of tools, devices and methods that have been used to obtain a sample of tissue from a patient, for testing and diagnosis of potential medical problems with the specific tissue or the patient in general. Attempts have been made to make the procedure as minimally-invasive as possible. To that end, needles have been developed which can be inserted through the skin of a patient directly or through the vasculature to a tissue mass or other particular location from which a sample is desired. Through mechanical or other means a sample is captured by the needle, and the needle is withdrawn with the sample.
Several difficulties with this type of needle have been noted over time. Many have utilized inner and outer cannulas that slide with respect to each other. Such devices make an opening through the patient of the outer diameter of the outermost cannula, while only obtaining a sample that is at most the width of the inner diameter of the innermost cannula. Thus, the opening that must be made in the patient is generally significantly larger than the size of the tissue sample, or conversely, for a desired amount of tissue, the opening to be made in the patient must be larger and consequently more uncomfortable. Similarly, some existing needles have suffered from difficulties in controlling or maintaining the tissue sample until it can be transferred to storage or analysis areas. Withdrawal of the needle can leave the tissue behind within the patient, particularly if the tissue must be pulled away from other tissue joined across its width.
Accordingly, there remains a need for a biopsy needle that is capable of obtaining a sample of a desired size while keeping the profile of the opening in the patient minimal, and/or is effective in maintaining the sample while allowing it to be easily removed from the needle into a storage or testing device.